These teachings relate generally to ion measurements.
In one exemplary embodiment, these teachings can be applied to measurement of small changes in calcification.
There is a need for measurement of small changes in calcification. For example, with ever-increasing amounts of carbon dioxide (CO2) entering the atmosphere, oceans are absorbing more and more CO2. Part of this CO2 becomes carbonic acid which dissolves in oceans, lowering pH levels. This phenomenon is known as ocean acidification which lowers the carbonate saturation states. A consequence of this phenomenon is that marine calcifying organisms, like corals, coralline algae, molluscs and foraminifera, have difficulties producing their skeletons and shells at current rates, with potentially severe implications for marine ecosystems, including coral reefs. In fact, there has been a recent research study by the U.S. Geological Survey on the effects of ocean acidification on crustose coralline algae (a cosmopolitan group of calcifying algae that is ecologically important in most shallow-water habitats). It was found that the recruitment rate and growth of crustose coralline algae were severely inhibited in the elevated carbon dioxide mesocosms. The calcification rates in reef-building corals may have slowed down by 10% over the last 150 year, with predictions to slow another 15-30% by the end of the century.
As can be seen from the table below, none of the existing methods for measuring calcification rates-measurement of total alkalinity and extraction of the calcification rate using equations based on certain assumptions, direct measurements of Ca+2 with an ion selective electrode and complexometric titration, are suitable and cannot meet the requirements for the needed calcium ion measurements.
There is a need for systems that can measure small changes in calcification (calcium ion measurements).
There is also a need for systems that can measure small changes in calcification in the presence of other interfering ions.
In other exemplary embodiments, there is a need for measurement of ions in applications including environmental monitoring as well as biological fields. These applications include detection of other ions such as magnesium, zinc, cadmium, copper, nickel, iron, arsenic, mercury, antimony, gold and other metal ions, including heavy metal ions, transition-metal ions and main-group ions.
TABLE 1Comparison of recent advances in detection of Ca+2Detection methodsAdvantagesDisadvantagesField effect transistorUltra sensitive Limited dynamic range(FET) based on Carbon(<1 nM)Small relative changenanotube (CNT)/probeGood selectivityin current atcompositeshigh concentrationsFluorescent fiber-opticGood sensitivitySmall dynamic rangesensor based on(~40 nM)(<0.1 mM)dye probeRapid responseComplex measurement(<1 second)Good selectivityMicrochip-based fiberGreat selectivityDoes not have highoptic (UV) detectionsensitivitytechniqueLow dynamic rangeElectrochemical sensorGood sensitivityLow dynamic rangebased on silicon Rapid responsenanowires modifiedwith phosphotyrosineMicrocantileversHigh sensitivityVery low dynamic rangemodified withGood selectivityVery sensitive to ion-selective self-mechanical disturbancesassembled monolayers(SAMs)